Thermal conduction mechanism of ferroelastic Zr-Y-Yb-Ta-Nb-O high- entropy oxides with glass-like thermal conductivity

Y Yao and GL Ren and YL Yu and JW Che and T Liang and L Li and YG Liu and F Yang and XF Zhao, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 105, 4360-4374 (2022).

DOI: 10.1111/jace.18374

Ferroelastic high-entropy oxides (HEOs) with high fracture toughness and low thermal conductivity are promising topcoat materials for next- generation thermal barrier coatings (TBCs). However, phonon transmission characteristics in the ferroelastic HEOs are less well understood due to their complicated and highly-disordered structure. Here we prepared two types of ferroelastic Zr-Y-Yb-Ta-Nb-O HEOs and investigated their thermal conduction behaviors at 100-900 degrees C. Hybrid Monte Carlo and molecular dynamic simulations were employed to understand the thermal conduction mechanism in this high-entropy system. Results show the HEOs present glass-like, low thermal conductivity (< 1.30 W m(-1) K-1 at 100 degrees C), which is attributed to the diffused lattice vibration mode with random polarization distribution. Dominant delocalized phonon modes in the HEOs are beneficial to strengthening phonon scattering and consequently decrease the thermal conductivity significantly. Lower thermal conductivity can be achieved by tailoring the composition and crystal structure of the HEOs to increase the contribution from diffused lattice vibration and "diffusion". This work provides a fundamental insight into the thermal conduction mechanisms of HEOs, which may facilitate materials design of low thermal conductivity materials for TBCs applications.

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